Abstract We present results of a 0.1-100 keV BeppoSAX observation of the
dipping low-mass X-ray binary (LMXRB) EXO 0748-676 performed in 2000 November.
During the observation EXO 0748-676 exhibited X-ray eclipses, type I X-ray bursts and
dipping activity over a wide range of orbital phases.
The 0.1-100 keV "dip-free"(i.e. dipping and eclipsing intervals excluded)
spectrum is complex,
especially at low energies where a soft excess is present. Two
very different spectral models give satisfactory fits. The first
is the progressive covering model, consisting of separately absorbed
black body and cut-off power law components. This model is
often used to study the dipping activity in LMXRB.
The second model is an absorbed cut-off power law together with a moderately ionized
absorber with a sub-solar abundance of Fe and a 2.13 keV absorption feature
(tentatively identified with Si XIII). This ionized absorber may
be the same feature as seen by Chandra during dips from EXO 0748-676.
The fact that these two physically very different models both give acceptable
fits to the data and plausible values of the best fit parameters
indicates how difficult it is to reliably model such complex
dipping spectra with moderate spectral resolution data.
The blackbody component required by the progressive covering
LMXRB model probably has a more complex underlying nature,
due to the strong effects of ionized absorption present.